The present invention relates to a method and system for performing well operations from a floating installation.
Normally a conventional rig up for performing operations in a well will be comprised of stacked up heave eliminators, which comprises means for keeping the tension in a riser with the movement of a floating vessel or a floating installation, surface flow tree (SFT), equipment for performing wire line or coiled tubing operations into the well or even drilling in the well as for instance through tubing drilling, and a surface blow out preventer (SBOP) on the rig floor as part of the conventional work over riser. There will in some instances also be arranged a telescopic element in the riser below the SBOP. For performing wire line or coiled tubing operations the riser string will normally be depressurized and the rig heave motions vs. the workover riser string are compensated by keeping the upper end of the riser string with the SBOP in relative position in relation to the vessel.
There is in the applicant's own Norwegian patent application No. 20075757 (from which a applicant's pending U.S. patent application Ser. No. 12/734,562 claims priority) described a system where the difficulties with using a pressurized telescopic joint in a high pressure riser and also the situation with having the SBOP located on the top of the riser above the telescopic joint, creating outlets for well fluids at high pressure at a deck creating a situation which is possibly hazardous for personnel working on the floating installation, is solved by positioning an upper workover riser package (UWRP), with means for closing off the passage in the riser and means for cutting any equipment extending down in to the riser, is arranged below a telescopic joint in the riser. The UWRP is thereby arranged to be in a fixed position relative the seabed. The riser is kept in tension by the tensioning system on the floating installation. As the UWRP may be regarded as an extension of the riser, the tension wires are connected to the top of the UWRP to avoid bending forces acting on the UWRP. The system in NO2007575 further describes a system where the UWRP comprises an interface for connection of different kind of workover equipment, such as equipment for performing coiled tubing operations or equipment for wire line operations.
One problem with this system is the need to have the UWRP configured to close the passage and shear equipment that may be present in the passage, resulting in the need to equip the UWRP with several kinds of equipment for the different activities to be performed in the well. Another element is that the valves and shearing functionalities within the UWPR sometimes needs to be replaced or repaired, then the whole riser configurations must be released and taken up on the floating installation.